DESCRIPTION (adapted from application): The Exposure Assessment Core will provide sample collection, analytical, and support services to the respective research Projects to enable investigators to make informed assignments of exposure to the study population. This will be accomplished through the direct collection of sampling information (staff operation of air sampling instrumentation, administration of survey instruments, or similar application). Studies with a need for direct or active sample collection of exposure information, such as those involving micro-environmental sampling at homes, schools, or athletic fields to achieve study objectives, will have those needs met by the Exposure Assessment Core. Examples of these types of measurements include size-fractionated particle measurements (PM10 or PM2.5) and specialized monitoring for criteria air pollutants (for NO2, O3, or CO). Collection of house dust specimens for antigen characterization and other potential allergenic material in the homes of asthmatic subjects will also be managed or directly performed by the Exposure Assessment Core personnel.